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(Nov Model.)

' E. B. STUART. METHOD 0P OBTAINING OXYGEN AND NITROGEN PROM AIR. No. 588,617 PatentedAug. 24,1897.

UNITED STATES "PATENT EE'TC ERNEST n. STUART, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE GENERAL GAS COMPANY, OF SAME PLACE,

METHOD OF OBTAINING OXYGEN AND NITROGEN FROM AIR.

SPECIFICATION forming part of Letters Patent No. 588,617, dated August 24, 1897.

Application filed April 1'7, 1896. Renewed December 24, 1896. Serial No. 616,946. (No specimens.)

.To all whom it may concern.-

Be it knownthat I, ERNEST B. STUART, a

citizen of the United States, residing at Chicago, in the county of Cook and State of 111i.-

nois, have invented certain new and useful Improvements in the Method of Obtaining Oxygen and Nitrogen, of which the following is a full, clear, and exact specification.

This invention relates generally to improvements in the method of obtaining oxygen and nitrogen from air by bringing the latter into contact with a preparation with which oxygen will combine and to which nitrogen is indifferent and therefore passes off and from which the oxygen may atterward be released when the preparation or substance is subjected to the influence of steam, thus leaving the ingredients of the substance in the form they were before having oxygen combined therewith; but more specifically my invention relates to the method of making oxygen and nitrogen producing substances containing oxid of manganese and caustic soda or containing a manganate of soda formed by the mixture of oxid of manganese and caustic soda. I p It has long been well known that the economical production of oxygen for commercial use would be of great commercial value, because of the capacity of oxygen for producing high temperatures and intense light in the combustion of other substances and gases, as well as for a multiplicity of uses in the arts and sciences and that the atmosphere or air is the most available and practical source from which to obtain it.

Nearly thirty years ago one Tessi du Motay discovered by laboratory investigations and therefrom at that time disclosed to man ganate of any form for the production of oxygen or nitrogen, although ever since Tessi du Motays discovery the desirability of manganate of soda forthat purpose has been recognized to a world-wide extent and numerous unsuccessful elforts have been made to so use it, as is shown by the literature on the subject.

N ow a mangauate of soda, accurately speaking, is formed by combining ten parts, by weight, ofcaustic soda with eleven parts of binoxid of manganese and eight parts of oxygen at a temperature of about 300 centigrade, and in forming at this temperature water separates out and is expelled and coincident therewith manganate of soda is formed, according to the following reaction:

300 Centigrade and above is brought in contact with said manganaie of soda a mutual decomposition takes place, andas a result oxygen is evolved,'leaving the original mixture of caustic soda and oxidof manganese.

A manganate of soda when so formed possesses marked advantages over any other agent for producing commercially oxygen and nitrogen for the reason that it will produce more oxygen per pound than can be produced at the present time from any other known agent; that caustic soda and oxid of manganese are found in commerce in a higher degree of purity, are cheaper and more available in large quantities than any other material for the production of a manganate; that caustic soda is less volatile than any other of the alkalies, and that theuse of binoxid of manganese facilitates the production of a manganate in that a manganate is thereby produced at one operation, while, on the other .hand, other oxids or salts of manganese are indirect, because more than one operation is required.

Theoretically upon the assumption that every molecule of any given body of a manganate of soda is exposed to steam and air every pound of chemically pure man ganate of soda is capable of yielding one cubic foot of oxygen for every reaction, but in practice this yield is impossible, because manganate IOO of soda is an impenetrable solid, and therefore this yield can only be proportionate to the surface of the manganate exposed to steam and air.

In efforts to successfully utilize a manganate of soda for producing oxygen a weight or bulk of it sufficient for commercial use has been reduced to particles or granules of a size permitting the free circulation of air and steam therethrough and by this means provide such a bull; of mangan'ate of soda with the largest possible extent of surface consistout with its solid form. Manganate of soda, however, is a salt soluble in water, and as steam is water it not only performs the chemical function of liberating oxygen from a manganate, but at the same time by its physical action dissolves the manganate, with the result that in the process as heretofore practiced the granules are rendered less and less solid after every reaction and the adjacent granules or particles caused to so quickly merge the one into the other that before any substantial volume of oxygen has been produced the multitude of granules have consolidated into a single viscid mass impenetrable to air and steam. This resulting impenetrability by air and steam and the deterioration of the surface at every reaction have heretofore so generally been recognized by others in efforts to successfully utilize Tessi du Motays discovery that various means have been devised for so disposing the manganate as to increase its surfaoe-namely, by placing the manganate in a number of shallow pans arranged one above the other in a retort; by

vcoating porous substances, such as pumicestone, with the manganate in the form of a viscid mass; by mixing it with infusible and insoluble substances, such as kaolin, and by first granulatin g the m auganate and then dusting it with oxid of copper; but none of these efforts have been successful for many reasons, among which may be mentioned that in the use of shallow pans it is practically impossible, with commercial economy, to raise their contents to the degree of heat necessary for manganate to successfully evolve oxygen, which expense, moreover, is increased by the untimely destruction of the only practical form of retort-namely, iron; that pumicestone is too poor a conductor of heat, while kaolin lacks the necessary porosity to enable the successful distribution of air and steam to the manganate therein contained, and that a coating of oxid of copper not only reduces the penetrability of the granules to air and steam, but, on the contrary, quickens their viscosity and, furthermore, does not contain suiiicient resistance to maintain the integrity of said granules, and as a resultthey very soon coalesce.

From the foregoing it will be understood that the manganese and the alkali or soda require a certain degree of heat to cause them to combine in the form of a manganate, and in so doing they absorb or combine with a certain amount of oxygen, and if this manganate is thereafter subjected to steam the oxygen is liberated or evolved from each molecule of the manganate with which the steam comes into contact, but this result cannot occur unless the mass be reduced to a practically non-volatile liquid, so that the steam may reach every molecule, and at the same time the consistency of the mass will be unchanged, and it is also evident that this liquefaction of the mass must occur at a temperature below that at which steam decomposes, because otherwise the steam when subjected thereto would be resolved by the heat into its component gases, which are incapable in such form of effecting the regeneration or reconversion of the man ganate into its uncombined ingredients and theconsequent liberation of the oxygen absorbed by or combined therewith, and on the other hand the temperature of the mass must be above that v at which steam forms, because otherwise the steam would be condensed, and henceprod uce the same objectionable result as water, as heretofore explained.

Therefore it is the object of myinvention, generally stated, to produce a preparation of any character which will absorb or combine with and liberate oxygen without physical change; to produce a preparation of any char acter which will freely combine with oxygen and as freely liberate the same under the influence of steam; to produce a practically liquid non-volatile preparation of any character which will combine with and liberate oxygen to produce a liquid preparation which will combine with and liberate oxygen without physical change; to produce a liquid preparation of any character from which oxygen can be liberated by the action of steam; to produce a preparation of such a character that every portion of any weight or bulk thereof shall be permanently accessible to a maximum degree to the alternate action of air and steam for an indefinite time withoutany reduction in the capacity of the active agent of said preparation, whereby oxygen may be produced by a regenerative process; to produce a. preparation which when subjected to air will combine with oxygen and liberate said oxygen when subjected to the influence of steam, leaving the chemical after its subjection to said steam in the physical condition it was before being subjected to air, whereby such alternate actions may be carried on indefinitely without deteriorating that property of the chemicals which enables them to absorb or combine with and liberate oxygen under the alternate influence of air and steam.

More specifically stated the object of my invention is to produce a preparation containing a manganate, the said preparation being of such a character that oxygen may be combined with every portion of the manganate contained in any quantity or body of said preparation and released therefrom by the action of steam and this alternate operation be repeated indefinitely without any deterioration or change in the consistency of the preparation, and as a result said preparation embraces all of the advantages due to the use of any manganate in the production of oxygen and with an absence of the disadvantages heretofore attending the use of the manganates, and, finally, to produce a preparation containing manganate of soda, the said preparation being of such a character that oxygen and steam may alternately be combined with every portion of the active principle thereof in any quantity or body of the said preparation and this operation be repeated indefinitely without any deterioration or change in the consistency of the preparation, whereby said preparation shall embrace all of the advantages of which a manganate of soda is capable in the production of oxygen and with an absence of all of the disadvantages heretofore attending its use.

Now to accomplish these objects I produce an oxygen-absorbing substance which may be maintained in a fused liquid state at a degree of temperature so low that when subjected to the action of steam in the process of producing oxygen from atmospheric air the steam Will'not be decomposed by the heat, but will efi'ectually perform its desired function of reconverting the oxygen-absorbing substance into its component ingredients or elements, and thereby liberate the oxygen from the fused mass and render the latter susceptible of again absorbing or combining with more oxygen.

After various ex-perimentsin efforts to successfully utilize a manganate of soda for producing oxygen and nitrogen I finally discovered that when to oxid of manganese there is added caustic alkali in a certain excess of that necessary for forming a manganate of soda and the temperature of this mixture is then raised to that at which the reaction occurs and the manganate is formed liquefaction takes place, and said liquid is ever afterward non-volatile and in physical form and chemical function is unchanged by the action of either air or steam, and as a result a preparation is produced in which manganate or the elements thereof are held permanently in a fused or liquid mass and in such form that every molecule thereof is permanently accessible to a maximum degree to the alternate action of air and steam, and thereby rendered capable of indefinitely absorbing or combining with oxygen to its fullest capacity and as completely releasing it and again absorbing more oxygen when subjected alternately to the influence of steam and air. This liquid man ganate will produce oxygen in a greater degree of purity than the same chemical in its solid form for the reason that the liquid possesses no interstices in which air can remain to act as a diluent, while on the other hand the interstices between the'particles of the chemical in its solid form retain air to such an extent that the production of pure oxygen is impossible without the adoption of some extraneous means for removing the air so retained; but in carrying out my invention I may employ any oxygen-absorbing substance, to which I add a sufficient quantity of w some fusible material that will be non-volatile at a temperature between that at which steam forms and that at which it decomposes by heat and will dissolve the said oxygenabsorbing substance and render the mass liquid at a temperature between the said extremes. This fusible substance may be any of the well known salts, either alkaline or neutral, as hereinafter described, or even an easily-f used metal or alloy,such as that known as the fools teaspoon, for instance, which isan alloy of bismuth, eight parts; lead, five parts, and tin, three parts; but I prefer to use an oxid of manganese or salt of manganese or some other compound of manganese which,when combined with alkali, will produce a manganate or perm an ganate,which constitutes the oxygen-absorbing substance, and as a solvent for dissolving and 1i quefyin g this I employ a sufficient quantity of any alkali or any of the neutral salts (which may be found suitable for producing a liquid manganate) to make the mass sufficiently liquid to enable the air and steam introduced therein while within the range of the abovenamed temperatures to intimately commingle therewith or permeate every particle thereof and evolve the oxygen therefrom. In practice, however, I have found it best to use for economy in the production of myliquid chemical about twenty-four parts, by weight, of commercial binoxid of manganese and about seventy-six parts, by weight, of commercial caustic soda, these proportions varying with I the impurities contained, but representing about twenty parts of binoxid of manganese chemically pure and about fifty-eight parts of pure caustic soda, for when this mixture is heated to about 300 centigrade there is thereby produced a liquid having a maximum capacity for minute commingling with steam and air and thereby separating the oxygen and nitrogen from the latter.

The formula Na2MnO,-l-(NaHO) will approximately express the relation between the sodic inanganate formed and the free or uncombined sodic hydrate remaining when these proportions are employed, and the reactions of decomposition and regeneration by which oxygen and nitrogen are separated can be and in regenerating the man gan ate under the influence of an air-blast So long as the caustic soda in excess of that sufficient to'form a manganate of soda bears such proportion to the manganate as to cause the mass to liquefy at a temperature below that at which steam decomposes by heat these proportions may be varied without departure from my invention; but the effect of increasing the alkali or other solvent for the oxygenabsorbing substance or manganate beyond that already specified is that fluidity is increased and the melting-point of the mass reduced, and this result is accomplished at the expense of retort-space and a reduced percentage of yield of oxygen to a given bulk or weight of the liquid compound; and if, on the other hand, the proportion of alkali or solvent is reduced and the liquid correspondingl y thickened then air and steam have not the same free access thereto without the employment of a higher degree of heat than is necessary for the reaction and without danger of necessitating that the substance, in order to be rendered fluid, be subjected 'to a degree of heat sufficient to decompose the steam, and if this degree be necessary to produce liquefaction the preparation cannot be employed for evolving oxygen from air be cause the separated gases of steam or water are incapable of regenerating the manganate into its component elements, and without such regeneration or reconversion the manganate has not the property of absorbing more oxygen nor of evolving that which it contains. Hence it is a matter of vital importance that the proportion of alkali in excess be such as to produce fluidity of the mass at a temperature below that at which steam decomposes, an example of one of the varying proportionscapable of accomplishing this result being, as before stated, about twentyfour parts, by weight,of bin oxid of manganese and seventy-six parts, by weight, of sodic hydrate, which yield a manganate and an excess of alkali equal ,to about the weight of l the manganate. In other words, while in theory one pound of chemically-pure manga nate of soda will yield one cubic foot of o'xy- 1 gen for each reaction this yield per pound of total bulk of my liquid compound is decreased in proportion as the excess of caustic alkali is added for the purpose of securing fluidity, l and hence any greater or lesser fluidity than 1 is absolutely necessary for-a maximum free 3 exposureof each and every molecule of the manganate to the action of air and steam is of no advantage.

As before stated, I prefer to use a caustic soda for the reason that it is found in commerce in a higher degree of "purity, is cheaper, is more available in large quantities, and

, less volatile than any of the other alkalies;

producing a liquid manganate. For the purposes, however, of the generic protection of my invention in its use of any form of manganese in connection with any of the Wellknown or suitable reagents for the produc-} tion of a liquid manganate I have filed, February 7 1896, another application, Serial No.

578,298, embracing and claiming the use of any of the neutral salts which when used with any manganate will produce a liquid manganate. I also prefer to use binoxid of manganese because of its cheapness, commercial purity, and that its use facilitates the production of the desired manganate, but my invention includes any other oxid ofmanganese which, when combined with alkali, will produce a manganate or permanganate. In practicing my invention the alkali and the manganese are placed in a suitable vessel and the temperature raised to the meltingpoint of the alkali, and as soon as liquefaction occurs an air-blast may be introduced to complete the formation of the manganate.

When using my compound for the production of oxygen and nitrogen, this vessel may also be provided with suitable means for the introduction of steam, but in practice I prefer, as soon as liquefaction takes place in an open vessel, to transfer the material to a retort provided with suitable means for alterterna-tely injecting air and steam through the liquid and to complete the formation of the manganate by first introducing an airblast; but the manganate may be formed and oxygen produced therefrom by the use of any vessel or vessels now or hereafter devised and suited for that purpose, it being understood that my invention is not limited to the use of any particular vessel or apparatus for producing liquid manganate or evolving oxygen therefrom.

As before intimated, my invention and discovery is also adapted for the production of nitrogen, to which end the nitrogen, being indifferent to the manganate, passes the same and may be conducted to a suitable holder or other storage vessel.

In the accompanying drawing is illustrated a vertical section of one of many suitable de vices for producing oxygen and nitrogen from a liquid man ganate, in which A indicates the walls of a furnace; B, a retort situated therein; 0, a liquid manganate in said retort; D, an air -supply pipe provided with a suitable valve (1, through which an air-blast may be introduced to the manganate; E, a discharge-pipe for the nitrogen provided with a valve 6; F, a steam-pipe provided with a valve f for the supply of steam to the manganate, and G an oxygenfdischarging pipe provided with a valve g.

In operating, the valve f in the steam-pipe and the valve g in the oxygen-discharging pipe are closed and the valve 6 in the nitrogen-discharging pipe is open during the blast of air through the pipe D, but as soon as the liquid manganate is fully charged with oxygen and after the poor air containing nitrogen has passedoif through the pipe E the valve 6 thereof is closed, as is also the valve 01 in the pipe D, and thereupon the valve f is opened and steam at the proper temperature, passing through the pipe F, discharges into the liquid mass, liberating the oxygen, which that liquefaction which exists without material volatilization at a temperature between i that at which steam forms (or that which will not condense steam) and that which decomposes steam, and I disclaim any intention of employing said terms in any such generic sense as to include chemicals mixed with or held in suspension in water, for I am aware that the aqueous form of manganate combined with free alkali is not new, nor do I wish to claim the same. It will also be noted that in describing my invention I employ the terms absorb and combine indifferently or indiscriminately with reference to the conduct of the so-called oxygen-absorbing substance upon the oxygen, or vice versa, for without attempting to decide whether the oxygen is actually combined with the preparation in a strict technical sense in every phase of my invention I regard the word absorb as the generic term including any function of the preparation which enables it to separate the component elements of air and cling to or retain one while the other passes off.

It is of course true that nearly all substances are more or less volatile at sufficient heat, but the term non-volatile is employed herein in its popular sense and does not embrace those substances which volatilize un der moderate heat, and particularly below the temperature at which steam forms.

Having thus described my invention, what I claim as new, and desire to secure byLetters Patent, is

1. The herein-described method of separating atmospheric oxygen and nitrogen, the same consisting in subjecting air to the action of a fusible chemical in liquid form, substantially as set forth.

same consisting in subjecting air to the action of the elements of a manganate in aliquid form, substantially as set forth.

4. The herein-described method of obtainin g oxygen the same consisting in subjecting air to the'action of the elements of a manganate in a fused and liquid form and then subjecting the manganate so formed to the ac tion of steam, substantially as set forth.

5; The herein-described method of separating atmospheric oxygen and nitrogen the same consisting in subjecting air to the elements of a manganate ofsoda in-a fused and liquid form, substantially as set forth..

6. The herein-described method of obtainin g oxygen, the same consistingin subjecting air to the elements of a manganate of soda in a fused and liquid form and then subjecting the manganate of soda so formed to the action of steam, substantially as set forth.

7. The herein-described method of separating atmospheric oxygen and nitrogen, which consists in fusing in the presence of air an oxygen-absorbingsubstance,atatemperature below the degree at which steam decomposes, and then subjecting the mass while in a fused and liquid form to the action of steam, substantially as set forth.

8. The herein-described method of separating atmospheric oxygen and nitrogen, which consists in fusing in the presence of air, an oxygen-absorbing substance, at a temperature below the degree at which steam decomposes and then subjecting the mass while in a fused and liquid form to the action of steam and afterward alternately to the action of air and steam, substantially as set forth.

'9. The herein-described method of separating atmospheric oxygen and nitrogen, which consists in heating the elements of a manganate in the presence of air .at a temperature between that at which a manganate forms and that'at which steam decomposes and in the presence of an admixture of fusible material sufficiently in excess to cause the mass to fuse and liquefy between said degrees of temperature, and then subjecting the mass while in a fused and liquid form, alternately to the influence of steam and air, substantially as set forth.

ERNEST B. STUART.

Witnesses i F. A. Horxms, EDNA B. JOHNSON. 

